changelog for dash[testing] loosening

Author: alexcjohnson

CHANGELOG.md

@@ -3,6 +3,9 @@ All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [UNRELEASED]
+### Changed
+- [#1503](https://github.com/plotly/dash/pull/1506) Fix [#1466](https://github.com/plotly/dash/issues/1466): loosen `dash[testing]` requirements for easier integration in external projects. This PR also bumps many `dash[dev]` requirements.
+
 ### Fixed
 - [#1493](https://github.com/plotly/dash/pull/1493) Fix [#1143](https://github.com/plotly/dash/issues/1143), a bug where having a file with one of several common names (test.py, code.py, org.py, etc) that imports a dash component package would make `import dash` fail with a cryptic error message asking whether you have a file named "dash.py"